Enhancing load bearing characteristics of compacted soil

ABSTRACT

Methods are disclosed for preparation of chemically-stabilized emulsions of tall oil in water. Temperature and pH are controlled during preparation of the emulsions so as to prevent saponification and neutralization of acids in the tall oil component. The final emulsions have pHs in the range of from about 3.0 to 5.0 and remain phase stable for extended periods of time. Methods are disclosed for using the emulsions for soil treatment to improve soil stabilization and load bearing capacity for roadbed use, for treatment of reclaimed asphalt pavement for reuse as a stabilized base course for roadway construction and for remediation of heavy metal contaminated soil.

This is a divisional application based upon co-pending U.S. patentapplication Ser. No. 08/819,594 filed Mar. 17, 1997 and now U.S. Pat.No. 5,895,347.

FIELD OF THE INVENTION

This invention relates to organic emulsions having water as thecontinuous phase of the type commonly used for soil stabilization. Moreparticularly, this invention relates to water phase emulsions comprisingtall oils, chemically stabilized with a blend of acid and an emulsifier.The pH of the water phase and the processing temperature are carefullycontrolled to prevent acid neutralization and/or saponification duringemulsification and to control the droplet size of the dispersed phase soas to prevent phase inversion. The emulsion can be used for thetreatment of soil to increase load bearing capacity and reduce dust andfor treatment of reclaimed asphalt pavement (RAP) to produce a productsuitable for use as a cold recycled asphalt pavement. The emulsions arealso useful for remediation of soil contaminated with heavy metals, suchas lead.

BACKGROUND OF THE INVENTION

It is well known that emulsions of tall oil and combinations of tall oilproducts with petroleum residues and/or natural asphaltites can beprepared. A wide variety of methods have been used for this purpose andnumerous methods are known to the art.

For example, emulsions prepared from blends of tall oil and/or tall oilpitch and naturally occurring or man made gilsonite are disclosed inU.S. Pat. No. 4,437,896, issued Mar. 20, 1984 to John F. Partanen.Additionally, U.S. Pat. No. 4,822,425 issued Apr. 18, 1989 to Richard M.Burch, discloses an emulsion comprising tall oil pitch, added rosin, anemulsifying agent and water. In both the Partanen and Burch patents, thepH and temperatures are not controlled during manufacture to preventsaponification or degradation of the acids or emulsion phase inversionfrom occurring.

Although various combinations of emulsions comprising tall oil are knownto the art, there still exists a need in the industry for improvedemulsions from tall oil, emulsified substantially free of other organiccomponents. In part this is due to changes in the paving industriesrequiring more stringent performance criteria, as well as to changingenvironmental requirements and changes in the quality of the availabletall oil products being supplied to the industry. Many existing methodsfor preparing emulsions of tall oil products cannot meet the new demandsof the paving industry.

The present invention is characterized by the fact that the pH andtemperatures during emulsion preparation are controlled to preventsaponification and neutralization of the fatty acids, resin acids andesters naturally occurring in tall oil products from occurring. Further,the emulsion is unique in that an emulsion is prepared without the needto add natural asphaltite or rosin to harden the end system or aid inemulsion stability. Emulsions prepared in accordance with the currentinvention can use standard refinery streams of tall oil products,without the need to adjust the streams with additional fatty acids orresin acids. The emulsions prepared in accordance with the currentinvention do not saponify or neutralize the acids or esters thereofcontained in the tall oil. Emulsions prepared in accordance with thecurrent invention thus are highly stable over extended periods ofstorage. The advantages of preserving the fatty acids and esters of thetall oil from saponification or neutralization are that the emulsionsremain better able to meet the performance requirements of the pavingindustry, as well as expanding their use to other industries.

SUMMARY OF THE INVENTION

It is, accordingly, the primary object of the present invention toprovide methods for preparing emulsions of tall oil products in such away that the fatty acids, resin acids and any associated esters thereofare not saponified or degraded during the process and the emulsions arehighly stable (i.e., base droplet size does not increase and phaseinvert). The emulsions created per the present invention are suitablefor use as an additive to soils for suppressing dust and increasing thebearing capacity of the soil. Other uses are as a binder in recycledasphalt pavement and in remediation of heavy metal contaminated soils.

DETAILED DISCLOSURE

As used herein, including the claims, "tall oil" includes man made andnaturally occurring tall oil, tall oil pitch, tall oil blends andsimilar tall oil products. Tall oil is the liquid resinous materialobtained in the digestion of wood pulp from paper manufacture.Commercial tall oils comprises a complex of fatty acids, resin acids,sterols, higher alcohols, waxes and hydrocarbons. The acid componentsalso may be present as the esters thereof. "Emulsions" as used hereinrefers to chemically stabilized emulsions with water as the continuousphase and tall oil as the dispersed phase. "Emulsifiers" refer tochemicals which reduce the surface tension between water and a liquidwhich normally is not water soluble or miscible, such as tall oil. Allpercentages are weight percentages by total weight, unless otherwisestated.

The acids typically found in tall oil are highly acidic. Saponificationof these acids typically occurs at pH levels above 6.5 to 7.0 andtemperatures above 72.0° C. (162° F.). Even at temperatures below 72.0°C., but pH levels above 6.5 to 7.0, saponification will occur, althoughmore slowly. Accordingly, in order to protect such acids and theirassociated esters against saponification, it is important to maintainemulsions prepared from tall oil at pH levels well below the 6.5 to 7.0threshold, and preferably in the range of from about 3.0 to about 5.0.Additionally, for extended shelf life of the emulsions, it is importantto control the percentage of dispersed phase in the emulsion. Emulsionsin which the dispersed phase exceeds about 55% to 60% typically willphase invert and become unstable, separating into two phases.Accordingly, it is preferred that the finished emulsions prepared inaccordance with the present invention have a dispersed phase (tall oil)content not exceeding approximately 50%, with the balance being aqueouscontinuous phase.

In the preparing emulsions in accordance with the present invention, astrongly acidic aqueous emulsifier solution is prepared, and thenblended with tall oil in order to prepare the finished emulsion. Apreferred composition for the emulsifier solution is approximately 4%emulsifier, 95.4% water and 0.6% acid. Preferred acids includehydrochloric acid and stearic acid. Preferred emulsifiers are anonylphenol/ethylene oxide mixture or lignin amine. Other emulsifiersalso can be used. It is desired that the emulsifier solution, onceprepared, be strongly acidic, in the range of about pH 1.0. Accordingly,the proportion of water and acid in the solution may be adjusted asneeded in order to obtain an emulsifier solution in this strongly acidicrange.

In preparing such emulsifier solutions, water (of quality suitable foremulsion manufacture) is heated to about 48° C., half of the acid isadded to the hot water, all of the emulsifier is added and thoroughlymixed and the remaining acid is added. The pH of the solution should beabout 1.0, if not, adjust to about 1.0 with additional acid.

Separately, the tall oil (preferably tall oil pitch) is heated to about126° C. Polymers, or other modifiers, if utilized, preferably are addedto the tall oil prior to or during the heating step.

The heated emulsifier solution and tall oil then are blended in ahomogenizer or a colloid mill to form the finished emulsion. Theblending rate is selected to prevent air entrainment or foaming fromoccurring. The ratio of the emulsifier solution to tall oil preferablyis such that the emulsion is about 50% tall oil and 50% emulsifiersolution; however, acceptable ranges are from about 40% to 60% tall oil,with the balance emulsifier solution. The finished emulsion preferablyhas a pH of from about 3.0 to about 5.0. If not, the acid content of theemulsifier solution can be adjusted to achieve the desired final pH.

The finished emulsion typically has a composition substantially asfollows:

    ______________________________________                                               Components                                                                            Percentage                                                     ______________________________________                                               water   47.70                                                                 acid    00.30                                                                 emulsifier                                                                            02.00                                                                 tall oil                                                                              50.00                                                                 Total   100.00                                                         ______________________________________                                    

Although the tall oil component in the emulsion preferably is no morethan about 50 to 55 weight percent, so as to prevent phase inversion andextend the shelf life of the emulsion, when used, the emulsion may befurther diluted with water to a desired application strength, since themore dilute emulsion resulting will be used promptly. Dilution of thefinished emulsion with an equal amount of water prior to applicationwould be typical.

Experimental

A series of emulsions were prepared in accordance with the proceduredisclosed above and tested as discussed below. The formulations and someresults are presented in Tables 1-A and 1-B:

                                      TABLE 1-A                                   __________________________________________________________________________                                          Solution                                                                          Tall Oil                            Emulsion                                                                           Tall Oil                                                                           Tall Oil                                                                            Emulsifier                                                                           Emulsifier                                                                         Acid  Solution                                                                          Temp.                                                                             Temp.                               Number                                                                             Source                                                                             Modifier                                                                            Type   Percentage                                                                         Type  pH  (° C.)                                                                     (° C.)                       __________________________________________________________________________    1    GP   None  Nonylphenol                                                                          1.00 None  7   48°                                                                        126°                         2    GP   None  Nonylphenol                                                                          1.50 None  7   48°                                                                        126°                         3    GP   None  Nonylphenol                                                                          2.00 None  7   48°                                                                        126°                         4    GP   None  Nonylphenol                                                                          1.00 HCl   4.00                                                                              48°                                                                        126°                         5    GP   None  Nonylphenol                                                                          1.50 HCl   3.00                                                                              48°                                                                        126°                         6    GP   None  Nonylphenol                                                                          1.50 HCl   2.00                                                                              48°                                                                        126°                         7    GP   None  Nonylphenol                                                                          1.50 HCl   1.00                                                                              48°                                                                        126°                         8    GP   None  Nonylphenol                                                                          1.50 HCl   1.00                                                                              48°                                                                        126°                         9    GP   None  Nonylphenol                                                                          1.50 HCl   1.00                                                                              48°                                                                        160°                         10   GP   None  Lignin Amine                                                                         1.50 HCl   1.00                                                                              48°                                                                        126°                         11   Az. Chem.                                                                          None  Nonylphenol                                                                          1.50 HCl   1.00                                                                              48°                                                                        126°                         12   Az. Chem.                                                                          None  Lignin Amine                                                                         1.50 HCl   1.00                                                                              48°                                                                        126°                         13   GP   None  Nonylphenol                                                                          2.00 HCl   1.00                                                                              48°                                                                        126°                         14   GP   None  Nonylphenol                                                                          1.50 Stearic Acid                                                                        1.00                                                                              48°                                                                        126°                         15   GP   Humic Nonylphenol                                                                          1.50 HCl   1.00                                                                              48°                                                                        160°                                   Acid                                                                16   GP   X-TOL 543                                                                           Nonylphenol                                                                          1.50 HCl   1.00                                                                              48°                                                                        126°                         17   GP   X-TOL 304                                                                           Nonylphenol                                                                          1.50 HCl   1.00                                                                              48°                                                                        126°                         __________________________________________________________________________     "GP" is a tall oil pitch supplied by GeorgiaPacific Resins, Inc. and          comprising a straight run vacuum tower bottoms stream produced from the       refining of crude tall oil obtained from a kraft paper process and            marketed under the trademark EXTOL.                                           "Az. Chem." is a similar tall oil pitch marketed by Arizona Chemical,         Panama City, Florida, under the trademark ACINTOL.                            "XTOL 543" is a variation of the XTOL tall oil pitch from GeorgiaPacific      Resins, Inc., containing approximately 39.4% resin acids and 51% fatty        acids.                                                                        "XTOL 304" is a variation of the XTOL tall oil pitch from GeorgiaPacific      Resins, Inc., containing approximately 1.6% resin acids and having an aci     number of 194.5.                                                         

                  TABLE 1-B                                                       ______________________________________                                               Tall Oil                                                                              Emulsion                                                       Emulsion                                                                             Percen- Temp.    Stability                                                                           Stability                                                                           Stability                                                                           Miscibility                         Number tage    (° C.)                                                                          24 Hour                                                                             5 Day 60 Day                                                                              In Water                            ______________________________________                                        1      50      71°                                                                             Fail  Fail  Fail  Fail                                2      50      71°                                                                             Fail  Fail  Fail  Fail                                3      50      71°                                                                             Fail  Fail  Fail  Fail                                4      50      71°                                                                             Fail  Fail  Fail  Fail                                5      50      71°                                                                             Pass  Pass  Fail  Fail                                6      50      71°                                                                             Pass  Pass  Fail  Fail                                7      50      71°                                                                             Pass  Pass  Pass  Pass                                8      55      71°                                                                             Pass  Pass  Fail  Fail                                9      60      71°                                                                             Fail  Fail  Fail  Fail                                10     50      71°                                                                             Pass  Pass  Pass  Pass                                11     50      71°                                                                             Pass  Pass  Pass  Pass                                12     50      71°                                                                             Pass  Pass  Pass  Pass                                13     50      71°                                                                             Pass  Pass  Pass  Pass                                14     50      71°                                                                             Pass  Pass  Pass  Pass                                15     50      71°                                                                             Pass  Pass  Pass  Pass                                16     50      71°                                                                             Pass  Pass  Pass  Pass                                17     50      71°                                                                             Pass  Pass  Pass  Pass                                ______________________________________                                    

In Tables 1-A, 1-B, the column "Emulsifier Percentage" and "Tall OilPercentage" refer to the weight percent of, respectively, the emulsifierand tall oil components in the finished, shelf-stable, emulsions."Solution Temperature" and "Tall Oil Temperature" refer to thetemperatures of the emulsifier solution and tall oil components justprior to mixture, while "Emulsion Temperature" refers to the temperatureof the finished emulsion immediately after mixing. The "Stability"columns for 24 hour, 5 day and 60 day periods refer to whether thefinished emulsion remains stable (does not phase invert) when stored atroom temperature for the indicated periods of time. "Miscibility inWater" refers to whether the finished emulsion, containing approximately50% emulsified tall oil, blends satisfactorily on a 1-to-1 basis withadditional water to form a more dilute emulsion for application uses.

Tests have demonstrated that the acid values or acid numbers for thefinished emulsions are comparable to those of the straight run tall oilused in preparing the emulsions, adjusted for their dilution in theemulsions and for the additional acid added in emulsifier solutions.This confirms that the acid values of the pre-emulsion tall oil arebeing preserved in the process of preparing the emulsions, rather thanbeing partially saponified or neutralized as an in prior art processes.

Emulsions in accordance with Emulsion No. 7 in Tables 1-A, 1-B, furtherdiluted with additional water prior to use, were used to treat test soilsamples in order to demonstrate utility of the emulsion as a soiltreatment to increase load bearing capacity and strength of road bedsoils. The emulsion was tested with a clayey soil, classified A-7 underthe AASHTO soil classification system, which rates soils A-1 to A-7, A-7being the worst. Soil samples were obtained from a site near theintersection of Warner and Greenfield Roads in Gilbert, Maricopa County,Ariz. The material is a clayey soil. Samples from 25 five-gallon bucketswere combined and sieved through a No. 4 sieve to remove any oversizematerial and to break up clumps, and then thoroughly mixed together. Thecombined soil material was then split by the quartering method back intothe five-gallon buckets for storage. This produced a uniform soil sampleused for all of the soil stability tests.

Hydrometer data indicated constituent components of the soil sample as:sand, from about 35% to 39%; silt from about 26% to 33%; and clay, fromabout 38% to 28%. Maximum density varied from 103 pcf. to 105.5 pcf.,and optimum moisture (the water content permitting maximum compactionand density of the soil) from approximately 18.5% to 21%. The liquidlimit (the most liquid the soil will hold) was 48, approaching that ofhigh plasticity or "fat" clay, the plasticity index was 30, and the clayis expansive. Clay mineralogy evaluation indicated that the clay isprimarily montmorillonite.

Marshall specimens (test plugs about 4 inches in diameter and 2% incheshigh) of emulsion-treated soil were prepared generally in accordancewith the "Proposed Asphalt Emulsion Cold Mix Design Method" obtainedfrom Akzo Nobel. Soil sample specimens were compacted at total liquidscontent near the optimum moisture content obtained by ASTM D698, "TestMethod for Laboratory Compaction Characteristics of Soil Using StandardEffort," Method A, approximately 20% total liquid by weight of soil.Marshall specimens were treated with an application emulsion produced bymixing the emulsion #7 of Table 1-A, 1-B with an additional quantity ofwater. The additional water added was varied so as to produce the weightpercent tall oil residue (measured on a moisture-free basis) in thesubstantially dry Marshall specimens shown in Table 2 (ranging from 0.5weight percent to 4.0 weight percent). Compaction effort consisted of 30blows per face as indicated in the referenced emulsion design procedure.Higher compactive efforts were found not to be feasible for specimensmade with the clay soil.

The emulsion treated Marshall specimens were cured in air atapproximately 25° C. overnight for 16 to 18 hours, then oven-cured at60° C. for 48 hours. Marshall stability tests were performed on 60° C.specimens, and the results and averages are shown in Table 2:

                  TABLE 2                                                         ______________________________________                                        CLAY SOIL TREATED WITH EMULSION #7                                            Marshall Stability, Lbs. and Flow, 0.01 IN                                    % Residue     Stability     Flow                                              ______________________________________                                        0.5           8800          20                                                              8800          21                                                              8800 Average  21 Average                                        1.0           5520          14                                                              5600          14.5                                                            5600          15.5                                                            5573 Average  15 Average                                        1.5           6200          19                                                              6200          21                                                              6200 Average  20 Average                                        2.0           4600          18.5                                                            4325          13                                                              4463 Average  16 Average                                        3.0           4050          12.5                                                            4250          16                                                              4500          13.5                                                            4267 Average  14 Average                                        4.0           5460          21                                                              5400          22                                                              5430 Average  21 Average                                        ______________________________________                                    

R-Value testing was performed in general accordance with California Test301, "Method of Test for Determination of the Resistance `R` Value ofTreated and Untreated Bases, Subbases and Basement Soils by theStabilometer." "R-Values" measure resistance to plastic deformation ofthe soil under imposed loads. R-Value testing is done on saturatedspecimens. Therefore, the emulsion treated Marshall specimens first wereprepared as discussed above and then air dried for 21 days, after whichthey were saturated with additional water prior to R-Value testing.

Table 3 tabulates the results. The first column shows the percentresidual tall oil (measured on a moisture-free basis) on the driedemulsion-treated Marshall specimens. The second column shows the amountof weight gained by the treated specimens upon water saturation,measured as a percent of the dry Marshall specimen weight. The thirdcolumn measures the R-Value of the saturated specimens.

                  TABLE 3                                                         ______________________________________                                                       Saturation Weight                                              % Residual Tall Oil                                                                          Increase (%)                                                                              R-Value                                            ______________________________________                                        0              --          8                                                                             (interpolated)                                     0.5            17.3        8                                                  1.0            19.4        9                                                  1.5            24.7        10                                                 2.0            26.2        23                                                 ______________________________________                                    

The results indicate a minimal R-Value increase at 1.5% or less residualtall oil, with a substantial increase to R-Value 23 at 2.0 weightpercent. This indicates that the preferred amount of emulsion used fortreating road bed soil should be selected to produce a tall oil residuein the treated soil (the portion of the soil actually wetted by theapplied emulsion/water solution) of approximately 2.0 weight percent orgreater, based on dry soil weight. The 2.0 weight percent residual talloil sample was further air dried and tested for R-Value on a dry basis,producing a very high R-Value of 90.

Accordingly, the tests demonstrate that the shelf-stable tall oilemulsions produced in accordance with the present invention are usefulas soil stabilizers for road bed construction and produce road bed soilsroughly comparable to those which would be produced by a surfaceapplication of a thin film of asphalt, tar, etc.

Reclaimed Asphalt Pavement

Emulsions prepared in accordance with the present invention also areuseful as binders for reclaimed asphalt pavement to produce a coldrecycled asphalt pavement mixture suitable for use in road bedconstruction. Recycled asphalt pavement, commonly referred to as "RAP,"is old asphalt concrete taken up from, or ground off of, existingroadways. Such material, treated with an appropriate binder, produces acold recycled PATENT asphalt pavement mixture suitable for use as astabilized base course for new road construction and for other pavingapplications. Prior art binders used for such reclaimed asphalt pavementmost commonly were aromatic emulsions, which served to soften the RAPand make it stick together when laid down under pressure, as with asteam roller. However, aromatics of all sorts, including aromaticemulsions, increasingly are deemed harmful to the environment and theiruse in open air applications is being restricted. A substantial markettherefore exists for other types of binders for RAP pavements which aresubstantially free of aromatic petroleum constituents.

The RAP material used in the test reported below had a sizedistribution, determined in accordance with ASTM C136 and ASTM C117 asfollows:

    ______________________________________                                        SIEVE        ACCUMULATIVE                                                     SIZE         % PASSING                                                        ______________________________________                                         6                                                                             4                                                                             3                                                                             2                                                                             11/2                                                                          11/8        100                                                               1           98                                                                 1/4        94                                                                 1/2        79                                                                 3/8        71                                                               No. 4        56                                                                8           46                                                                10          34                                                                16          31                                                                30          22                                                                40          10                                                                50          7                                                                100          5                                                                Finer Than   3.3                                                              No. 200                                                                       ______________________________________                                    

Sample mixtures of such RAP were admixed with samples of finishedemulsion no. 13 of Table 1-A,1-B above at varying emulsion amounts equalto 2, 3 and 4 weight percent emulsion, based upon the dry weight of RAP.Finished emulsion no.13 was admixed with sufficient water, prior toblending with the RAP sample, to maintain a constant mixing fluids(mixing water plus emulsion) content of 6 weight percent mixing fluidsbased upon the dry weight of RAP, for each of the 2, 3 and 4 weightpercent emulsion levels tested.

Three sets of Marshall specimens were prepared from the 2, 3 and 4weight percent emulsion/RAP mixtures and were tested using the Marshallmethod (ASTM D1559). Fifty compaction blows were applied per Marshallspecimen phase at an angle of 75±5°. Following compaction, the specimenswere left in their molds and oven cured at 49° C. for 24 hours. Theywere then extruded, placed on glass plates and again oven cured at 49°C. for an additional 24 hours. After final curing, the specimens werecooled to 25° C. and tested for height, density, Marshall stability andflow. Examination of the specimens after the Marshall stability testsindicated that binder distribution and aggregate coating appearedsatisfactory for each of the 2, 3 and 4 percentages mixtures. Theresults of Marshall stability tests on the samples are presented inTable 4 below:

                  TABLE 4                                                         ______________________________________                                                EMULSION            SPECIMEN                                                                              MARSHALL                                  SPECIMEN                                                                              CONTENT   DENSITY   HEIGHT  STABILITY                                 NUMBER  %         (pcf)     (in)    (lbs.)                                    ______________________________________                                        1       2.0       117.6     2.438   4150                                      2       2.0       117.6     2.458   3920                                      3       2.0       117.6     2.480   4060                                      --      Average   117.6     --      4043                                      4       3.0       117.3     2.495   3050                                      5       3.0       117.8     2.476   3200                                      6       3.0       117.8     2.473   3320                                      --      Average   117.5     --      3190                                      7       4.0       117.8     2.490   2600                                      8       4.0       118.7     2.478   2650                                      9       4.0       118.5     2.468   2650                                      --      Average   118.3     --      2633                                      ______________________________________                                    

In Table 4 the "average" line shows, respectively, for the 2%, 3% and 4%samples tested, the average density and average Marshall stability,measured in pounds, of the samples tested. The Asphalt Institutespecifications for RAP used as cold recycled asphalt pavement specifies750 lbs. or better Marshall stability for light traffic, 1200 lbs. orbetter Marshall stability for medium traffic and 1800 lbs. or betterMarshall stability for heavy traffic road bed usage of such pavements.Accordingly, the tested stability for emulsion treated RAP samples allproduced Marshall stability ratings which meet or exceed those requiredby the Asphalt Institute for use of such materials in road bed paving.Further, the tests demonstrate that an emulsion content of approximately2%, based upon dry RAP weight, produces the highest Marshall stabilityrating of those samples tested. Since the emulsion no. 13 is 50% talloil, 2% emulsion, based on the dry weight of RAP, represents acontribution of approximately 1% tall oil, measured on a water-freebasis, to the RAP/emulsion mixture.

Soil Remediation

An additional use of emulsions prepared in accordance with the presentinvention is for remediation of soil contaminated with heavy metals,especially lead. Capillary and hydraulic flows of water in porous mediacontaminated by heavy metal species, has resulted in aquifercontamination. Removal of heavy metals from the contaminated soil isenergy intensive and time consuming, since the mobility of heavy metalions such as lead is orders of magnitude slower in soil than in water.Remediation of the soil by chemical treatment which binds the metalcontaminants in place, so that they will not leach out of the soil, hasthe potential for substantial cost savings, while producing significantenvironmental benefits.

Utility of emulsions in accordance with the present invention for use assoil remediation additives was demonstrated by comparing leadcontamination measurements of soils spiked with 1,000 parts per millionlead with the same lead contaminated soil treated with 1% of finishedemulsion no. 12 of Table 1-A, 1-B above. Four soil samples were testedfor total lead, STLC lead and TCLP lead as follows:

                  TABLE 5                                                         ______________________________________                                                         Total STLC     TCLP                                                           Lead  Lead     Lead                                          ______________________________________                                        Soil (no lead)     14      --       --                                        Soil (with 1,000 ppm lead added)                                                                 660     66       4.2                                       Soil (with 1,000 ppm lead added) plus                                                            760     62       2.6                                       1% Emulsion No. 12                                                            Soil (no lead) plus 1% Emulsion No. 12                                                           11      0.5      <0.5                                      ______________________________________                                    

In Table 5, total lead was determined by EPA test 6010, STLC lead wasdetermined by EPA test method 6010 and TCLP lead was determined by EPAmethods 1311/6010. The STLC lead and TCLP lead are both U.S.Environmental Protection Agency ("EPA") tests which measure lead leachedfrom soil under test conditions, in order to approximate the amount oflead in the soil which is available for leaching into the environment.The 2.5 TCLP lead measured for the lead contaminated soil treated with1% emulsion no. 12 is sufficiently low that such soil would not requireadditional remediation for most purposes, while the 4.2 TCLP leadmeasured for the untreated sample would require remediation.Accordingly, a suitable method for remediating lead contaminated soilfor compliance with EPA requirements would comprise removing thecontaminated soil, admixing it with 1% or more by weight of an emulsionprepared in accordance with the present invention (representingapproximately 0.5 weight percent of tall oil on a moisture free basis)and returning the emulsion treated soil to place or removing it toanother site for disposal.

The foregoing disclosure and description of the invention areillustrative only, and various changes may be made in the emulsioncomponents, methods of formulation and application, within the scope ofthe appended claims, without departing from the spirit of the invention.

What is claimed is:
 1. A method for enhancing the load-bearingcharacteristics of compacted soil comprising applying to said soil anemulsion, said emulsion comprising (1) tall oil; (2); water; (3) acid;and (4) an emulsifier, said emulsion having a pH in the range of about3.0 to 5.0 and having tall oil as its major hydrocarbon-containingcomponent, with said tall oil and water, combined, comprising amajority, by weight, of said emulsion.
 2. The method according to claim1 wherein said emulsion adds to the portion of said soil wetted by saidemulsion a quantity of said tall oil equal to or exceeding approximately2% of the dry weight of said portion of said soil wetted by saidemulsion.
 3. A method for enhancing the load-bearing characteristics ofcompacted soil comprising adding to said soil an emulsion comprising theemulsified admixture of(1) an emulsifier solution comprising water, acidand an emulsifier, said emulsifier solution having a pH of about 1.0;and (2) tall oil,said emulsion having a pH of from about 3.0 to 5.0 andhaving tall oil as its major hydrocarbon-containing component and withsaid tall oil and water, combined, comprising a majority, by weight, ofsaid emulsion.
 4. The method according to claim 3 wherein said emulsionadds to the portion of said soil wetted by said emulsion a quantity ofsaid tall oil equal to or exceeding approximately 2% of the dry weightof said portion of said soil wetted by said emulsion.